Executive function impairments have been identified in children with poor motor skills, with and without a diagnosis of developmental coordination disorder (DCD). However, most studies are cross-sectional. This study investigates the development of executive function in children with poor motor skills over 2 years. METHOD: Children aged 7 to 11 years (n=51) were assessed twice, 2 years apart, on verbal and nonverbal measures of executive functions: executive-loaded working memory (ELWM); fluency; response inhibition; planning; and cognitive flexibility. Typically developing children (n=17) were compared with those with a clinical diagnosis of DCD (n=17) and those with identified motor difficulties (n=17) but no formal diagnosis of DCD. RESULTS: Developmental gains in executive function were similar between groups, although a gap between children with poor motor skills and typically developing children on nonverbal executive functions persisted. Specifically, children with DCD performed significantly more poorly than typically developing children on all nonverbal executive function tasks and verbal fluency tasks at both time points; and children with motor difficulties but no diagnosis of DCD showed persistent executive function problems in nonverbal tasks of ELWM and fluency. INTERPRETATION: Children with DCD and motor difficulties demonstrated executive function difficulties over 2 years, which may affect activities of daily living and academic achievement, in addition to their motor deficit. WHAT THIS PAPER ADDS: Executive function difficulties in children with poor motor skills persist throughout middle childhood. Children with motor difficulties, without a developmental coordination disorder (DCD) diagnosis, demonstrate less pervasive executive function difficulties than those with DCD. Executive function problems in the groups with motor difficulties and DCD affect mostly nonverbal domains. All groups showed similar developmental gains in executive function. CI - (c) 2017 Mac Keith Press.